title: Country-wide assessment of the genetic polymorphism in Plasmodium falciparum and Plasmodium vivax antigens detected with rapid diagnostic tests for malaria.
abstract: BACKGROUND
  Rapid diagnostic tests (RDTs) are becoming increasingly indispensable in malaria management, as a means of increasing the accuracy of diagnosis. The WHO has issued recommendations, but the selection of the most suitable RDT remains difficult for users in endemic countries. The genetic variability of the antigens detected with RDTs has been little studied, but may affect the sensitivity of RDTs. This factor has been studied by comparisons between countries at continental level, but little information is available concerning antigen variability within a given country.
  
  
  METHODS
  A country-wide assessment of polymorphism of the PfHRP2, PfHRP3, pLDH and aldolase antigens was carried out in 260 Plasmodium falciparum and 127 Plasmodium vivax isolates, by sequencing the genes encoding these antigens in parasites originating from the various epidemiological strata for malaria in Madagascar.
  
  
  RESULTS
  Higher levels of polymorphism were observed for the pfhrp2 and pfhrp3 genes than for the P. falciparum and P. vivax aldolase and pldh genes. Pfhrp2 sequence analysis predicted that 9% of Malagasy isolates would not be detected at parasite densities < or = 250 parasites/mul (ranging from 6% in the north to 14% in the south), although RDTs based on PfHRP2 detection are now recommended in Madagascar.
  
  
  CONCLUSIONS
  These findings highlight the importance of training of health workers and the end users of RDTs in the provision of information about the possibility of false-negative results for patients with clinical symptoms of malaria, particularly in the south of Madagascar.
authors.affiliation: Malaria Research Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar. xnach@caramail.com
authors.forename: Natacha
authors.initials: N
authors.lastname: Mariette
authors.forename: Céline
authors.initials: C
authors.lastname: Barnadas
authors.forename: Christiane
authors.initials: C
authors.lastname: Bouchier
authors.forename: Magali
authors.initials: M
authors.lastname: Tichit
authors.forename: Didier
authors.initials: D
authors.lastname: Ménard
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics*; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D005188:False Negative Reactions; D006801:Humans; D008270:Madagascar; D008288:Malaria / Q000469:parasitology; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000235:genetics* / Q000302:isolation & purification; D010966:Plasmodium vivax / Q000235:genetics* / Q000302:isolation & purification; D011110:Polymorphism, Genetic; D015800:Protozoan Proteins / Q000235:genetics; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA
chemical_list: D000953:Antigens, Protozoan; D016054:DNA, Protozoan; C514457:HRP-2 antigen, Plasmodium falciparum; D015800:Protozoan Proteins; D011933:Reagent Kits, Diagnostic